Woods cooper Pipe measuring reference

[tmunn]

Guys, on the woods cooper .21 pipe would anyone have a picture or diagram on where they are measuring to on this pipe .Is it the middle of the flat band or 1/2 way between the back side of the weld and where it tapers down and sweeps forward.

In other words I have heard to use the middle of the band so does that include the weld and a pic or drawing or diagram would be awesome.

Thanks

Terry

 

[Chris Wood]

7 7/8 to the weld ( with the guage my father sells )

or inline with a ruler about 3 inches to the weld

 

[tmunn]

I have a plastic gage here but i am not sure who makes it.I have been measuring to the middle of the flat spot with it.I will have to see if i can get a picture of it.It has a hole in the plastic for the top of the glow plug to sit in and has a line on that follows the exhaust travel.

3" from the center of the engine Chris...Re glow plug

 

[Brian Sorgente]

I think the rule of thumb is to measure from the center of the cylinder to the start of the convergent cone. That's what I do anyway... At the end of the day its just a reference point.

Brian

 

[Grimracer]

I think the rule of thumb is to measure from the center of the cylinder to the start of the convergent cone. That's what I do anyway... At the end of the day its just a reference point.

Brian

What I have found is thats not 100% true. Header lenght can also play a part in the tune as well as where you cut the pipe.. The woods gauge can be used for that too!

Grim

 

[Brian Sorgente]

I think the rule of thumb is to measure from the center of the cylinder to the start of the convergent cone. That's what I do anyway... At the end of the day its just a reference point.

Brian

What I have found is thats not 100% true. Header lenght can also play a part in the tune as well as where you cut the pipe.. The woods gauge can be used for that too!

Grim

The point I was trying to make is that you can measure the pipe from anywhere you want on the boat. For the sake of comparing numbers its good that we keep the points that we measure from consistent but there is no "right place to measure to on the pipe" per say (at least I dont think there is). I always thought when people referred to a particular pipe length they meant the distance from the center of the cylinder to the beginning of the convergent cone, running along the center line of the header.

You bring up an interesting point though, I remember reading something a long time ago about how to determine the header pipe length. Something like X amount header pipe inside diameters added together should equal your header pipe length? What kind of relationship have you found that works well on our engines?

Brian

 

[shoboat]

Terry,

You would like to keep your header length as short as possible.

The gases want to expand as soon as they can out of the exhaust

port. If you can find a header that tapers that would be even better.

What some are using is Outboard pipes that have the curve already

built into the pipe.

Good Luck Testing,

Mark

 

[tmunn]

Greg, I did not receive a plastic gauge with my pipe from steve.I am borrowing this gauge from My friend dan who has not run nitro for a few years now.I would like him to run it again so we can play with riggers but he is enjoying gas boats .Also I am down to only two nitro boats and gas has taken over so I would not want him to get back into nitro and then me leave it.

Thanks guys i am going to get pics but from what i can tell I am bang on Chris's numbers with a tape or this gauge.Be back later.

 

[tmunn]

O-k, here is the gage i have and two measurement that I used .One with the gauge and one with the tape and straightedge.I would say I am very close to being where I need to be.Does anyone know of a better clamp than zipties and has anyone ever added a ring of something like jb weld to the header or pipe to keep the pipe from slipping in the exhaust coupler or JB an aluminum "ring" to the pipe or header for the same purpose.

I had to cut the installed ring on the pipe off to get the header inside the pipe to get it short enough and still have a bit of straight area on my header for the zip tie.

I know what you guys are saying about the OB pipe but I Have this stuff already and it seems to work fine .Just checking to see how it compares to other setups and maybe a couple slight changes.

 

[shoboat]

Terry,

That pipe works great at 7&5/8" don't be afraid to push it in from

8" where it is now. The rpm will increase and so will your speed.

You may have to back down the cup more,but most are running

too much cup for good rpm anyways.

Enjoy Testing,

Mark Sholund

 

[steve wood]

O-k, here is the gage i have and two measurement that I used .One with the gauge and one with the tape and straightedge.I would say I am very close to being where I need to be.Does anyone know of a better clamp than zipties and has anyone ever added a ring of something like jb weld to the header or pipe to keep the pipe from slipping in the exhaust coupler or JB an aluminum "ring" to the pipe or header for the same purpose.

I had to cut the installed ring on the pipe off to get the header inside the pipe to get it short enough and still have a bit of straight area on my header for the zip tie.

I know what you guys are saying about the OB pipe but I Have this stuff already and it seems to work fine .Just checking to see how it compares to other setups and maybe a couple slight changes.

you shouldn't have removed the ring.use one of the molded silicone car couplers and butt the header to the pipe.also you are not measuring the pipe correct.run your tape parellel with the pipe and come off the tape 90°to the plug,which will show that you are about 3 5/16 to 3 3/8from plug using this method,way long.try and tuck the pipe in so it runs parallel with the tub,yeah i know you have to cut the cowl and don't want to

 

[tmunn]

Guys,

I need to correct something I went to check to make sure since it has been a while .I did not cut off the ring on the pipe I only cut up to it.I need to pay more attention...lol....

Steve could you post a picture i don't follow you.I thought I was coming off the plug at 90* and measuring to the weld.I used the steel ruler only to illustrate this.Is the plastic gauge different from the one your dad sells.

I am getting confused over such a simple thing. :wacko:

Do you have a place to buy these car coupler ?

 

[steve wood]

Guys,

I need to correct something I went to check to make sure since it has been a while .I did not cut off the ring on the pipe I only cut up to it.I need to pay more attention...lol....

Steve could you post a picture i don't follow you.I thought I was coming off the plug at 90* and measuring to the weld.I used the steel ruler only to illustrate this.Is the plastic gauge different from the one your dad sells.

I am getting confused over such a simple thing. :wacko:

Do you have a place to buy these car coupler ?

this is steve,i'm the one that sells the gauge,orginally made by mike z.in the second pic you have the steel rule 90° to the yellow tape(correct) but the yellow tape should line up parrellel with the pipe,like you have it in the last pic

 

[aaron alberico]

Terry,

That pipe works great at 7&5/8" don't be afraid to push it in from

8" where it is now. The rpm will increase and so will your speed.

You may have to back down the cup more,but most are running

too much cup for good rpm anyways.

Enjoy Testing,

Mark Sholund

Mark

What do you class as to much cup to turn good rpm's?

Regards Aaron

 

[tmunn]

steve, pm me your number please ?

 

[tmunn]

What is the shortest you guys would think i would need to go.I should mention too for those that don't know ...I only use 50% nitro.

I ask what would be the shortest because i have made an aluminum ring aprox 3/32" wide and 1/16" high and am going to jb weld it onto the header so the coupler material will not slip.I figure with this ring and the ring on the pipe it should be fine.I just do not want to install the ring too close to the end of the header and be limited on how far forward i can push the pipe.

I also did as suggested and cut my cowl so the pipe can be mounted straighter as well as I am going to use a thinner walled coupler i found in my spare parts that has a thinner wall than the others I have so the pipe will fit much closer to the engine.

I will also make a new pipe bracket since this one is a tad short now with the pipe being farther ahead.

Thanks for the help so far guys.

 

[steve wood]

What is the shortest you guys would think i would need to go.I should mention too for those that don't know ...I only use 50% nitro.

I ask what would be the shortest because i have made an aluminum ring aprox 3/32" wide and 1/16" high and am going to jb weld it onto the header so the coupler material will not slip.I figure with this ring and the ring on the pipe it should be fine.I just do not want to install the ring too close to the end of the header and be limited on how far forward i can push the pipe.

I also did as suggested and cut my cowl so the pipe can be mounted straighter as well as I am going to use a thinner walled coupler i found in my spare parts that has a thinner wall than the others I have so the pipe will fit much closer to the engine.

I will also make a new pipe bracket since this one is a tad short now with the pipe being farther ahead.

Thanks for the help so far guys.

tried that too.that area is to close to the motor.probably close to 600 degrees.it melts the epoxy

319-752-4482

 

[Jeff Barnhart]

What is the shortest you guys would think i would need to go.I should mention too for those that don't know ...I only use 50% nitro.

I ask what would be the shortest because i have made an aluminum ring aprox 3/32" wide and 1/16" high and am going to jb weld it onto the header so the coupler material will not slip.I figure with this ring and the ring on the pipe it should be fine.I just do not want to install the ring too close to the end of the header and be limited on how far forward i can push the pipe.

I also did as suggested and cut my cowl so the pipe can be mounted straighter as well as I am going to use a thinner walled coupler i found in my spare parts that has a thinner wall than the others I have so the pipe will fit much closer to the engine.

I will also make a new pipe bracket since this one is a tad short now with the pipe being farther ahead.

Thanks for the help so far guys.

Shorten the pipe until the boat does not run consistently anymore, then pull it out an 1/8 to a 1/4 inch.

 

[shoboat]

Aaron,

Anything more than 3.75" is probably too much.

You can go over 80 MPH with 3.46" to 3.60".

You just need to add the right amount of pitch

in the center of the blade.

Thanks

Mark

 

[tmunn]

Steve, I sent you a pm.

I tried the pipe at 7-3/4 to the weld and that went fine so then I went and tried it at 7-5/8 and that went fine too so next time out i may try it shorter just for fun.It never took any plugs out and would slow down and then come up to speed after milling around at slower speeds.It seems to be working fine and i cut mu cowl to get the pipe closer to the cowl and parallel with the cowl .I will leave it alone until i test some new props from Mark .It think it will go better with a 1450 similar to what I had.